Question: $ A = \left[\begin{array}{rrr}2 & 2 & 1 \\ 2 & 1 & 1 \\ 1 & 1 & 0\end{array}\right]$ What is $ A^{-1}$ ?
$ = \left[\begin{array}{rrr}-1 & 1 & 1 \\ 1 & -1 & 0 \\ 1 & 0 & -2\end{array}\right]$